"Although emotions, or feelings, are the most significant events in our lives, there has been relatively little contact between theories of emotion and emerging theories of consciousness in cognitive science," the authors write.

Established theories state that emotions are "innately programmed" in the deeper parts of the brain below the outer cortex layer, such as the limbic system, which includes the amygdala, thought to be crucial in emotion. Emotions are conscious states that can be explained by higher-order theory, one of the dominant theories of consciousness.

They argue that emotional and non-emotional conscious experiences differ not in where they originate in the brain, but by their triggers.

"We argue that conscious experiences, regardless of their content, arise from one system in the brain," the authors, led by psychiatrist Joseph LeDoux of New York University's Center for Neural Science and founder of the Emotional Brain Institute, write in the paper.

This system is the cortex, the outer wrinkly layer of the brain, the authors say, and emotions can be seen as higher-order states in this region. However, the deeper parts of the brain still play an essential role in emotion, the authors say, as the cortex is often fed by inputs from brain regions such as the amygdala.

Focusing on the case study of fear as an emotion, the authors note that some types of emotion do not always rely on being fed by inputs from deeper parts of the brain, suggesting that the cortex plays a more prominent role in emotion than previously acknowledged.

"Existential fear/anxiety about the meaningless of life or the eventuality of death may not engage survival circuits at all. Our theory can thus potentially account for all forms of fear: those accompanied by brain arousal and bodily responses and those that are purely cognitive and even existential," they write.